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Combining mulch and irrigation scheduling may lead to an increase of crop yield and water use efficiency (WUE=crop yield/evapotranspiration) with limited irrigation water, especially in arid regions. Based on 2 years’ field experiments with ten irrigation-mulching treatments of spring wheat (Triticum aestivum L.) in the Shiyang River Basin Experiment Station in Gansu Province of Northwest China, a simulation based optimization model for deficit irrigation scheduling of plastic mulching spring wheat was used to analyze optimal irrigation scheduling for different deficit irrigation scenarios. Results revealed that mulching may increase maximum grain yield without water stress by 0.4-0.6 t ha(-1.) in different years and WUE by 0.2-0.3 kg m(-3) for different irrigation amounts compared with no mulching. Yield of plastic mulching spring wheat was more sensitive to water stress in the early and development growth stages with an increase of cumulative crop water sensitive index (CCWSI) by 42%, and less sensitive to water stress in the mid and late growth stages with a reduction of CCWSI by 24%. For a relative wet year, when irrigation water is only applied once, it should be at the mid to end of booting growth stage. Two irrigations should be applied at the beginning of booting and heading growth stages. The irrigation date can be extended to the beginning of jointing and grain formation growth stages with more water available for irrigation. For a normal or a dry year, the first irrigation should be applied 5-8 days earlier than the wet year. The highest WUE of 3.6 kg m(-3) was achieved with 180 mm of irrigation applied twice for mulching in a wet year. Combining mulch and optimal deficit irrigation scheduling is an effective way to increase crop yield and WUE in arid regions. (c) 2017 Elsevier B.V. All rights reserved.